Antibiotic Resistance, Virulence Gene Detection, and Biofilm Formation in Aeromonas spp. Isolated from Fish and Humans in Egypt

Abstract

The genus <i>Aeromonas</i> is widely distributed in aquatic environments and is recognized as a potential human pathogen. Some <i>Aeromonas</i> species are able to cause a wide spectrum of diseases, mainly gastroenteritis, skin and soft-tissue infections, bacteremia, and sepsis. The aim of the current study was to determine the prevalence of <i>Aeromonas</i> spp. in raw fish markets and humans in Zagazig, Egypt; identify the factors that contribute to virulence; determine the isolates' profile of antibiotic resistance; and to elucidate the ability of <i>Aeromonas</i> spp. to form biofilms. The examined samples included fish tissues and organs from tilapia (<i>Oreochromis niloticus</i>, n = 160) and mugil (<i>Mugil cephalus</i>, n = 105), and human skin swabs (n = 51) and fecal samples (n = 27). Based on biochemical and PCR assays, 11 isolates (3.2%) were confirmed as <i>Aeromonas</i> spp. and four isolates (1.2%) were confirmed as <i>A. hydrophila</i>. The virulence genes including haemolysin (<i>hyl A</i>) and aerolysin (<i>aer</i>) were detected using PCR in <i>A. hydrophila</i> in percentages of 25% and 50%, respectively. The antimicrobial resistance of <i>Aeromonas</i> spp. was assessed against 14 antibiotics comprising six classes. The resistance to cefixime (81.8%) and tobramycin (45.4%) was observed. The multiple antibiotic resistance (MAR) index ranged between 0.142-0.642 with 64.2% of the isolates having MAR values equal to 0.642. Biofilm formation capacity was assessed using a microtiter plate assay, and two isolates (18.1%) were classified as biofilm producers. This study establishes a baseline for monitoring and controlling the multidrug-resistant <i>Aeromonas</i> spp. and especially <i>A. hydrophila</i> in marine foods consumed in our country to protect humans and animals.